I. Field of the Invention
The present invention is directed generally to improvements in high energy propellant compositions, particularly with regard to the use of alternate ingredients to improve energetic qualities and increase bulk loading density without increasing impact, shock or friction sensitivity. More particularly, the invention allows the use of a relatively large amount of 1,3,5-trinitro-1,3,5-triaza-cyclohexane (cyclo trimethyl trinitramine) usually referred to as cyclonite or (RDX) in double-based compositions to increase energy output and achieve greater bulk loading densities without increasing impact, shock or friction sensitivity by adding the RDX in combination with an amount of nitrato ethyl nitramines (NENAs) as ingredients in the high energy propellants. In this manner, greater bulk loading densities and energy outputs are achieved without additional risk. The invention is particularly suitable for granular loaded tank ammunition.
II. Related Art
Most conventional propellants including propellants used in conventional artillery including 120 mm tank ammunition, and particularly those that are poly-based, use a matrix component, usually nitrocellulose (NC), in combination with nitroglycerine (NG), which also acts as a high energy plasticizer for the NC, together with an amount of an energy adjusting component such as an energetic solid exemplified by cyclo trimethyl trinitramine (RDX), cyclo tetramethyl trinitramine usually referred to as homocyclonite or (HMX), ethylene di-nitramine (EDNA), and others. Diethylene glycol dinitrate (DEGDN) and triethylene glycol dinitrate (TEGDN) are also employed as conventional primary high energy adjustment components. However, the use of these materials in propellant formulae is discouraged because, while these materials enable a propellant to obtain and maintain a high energy level, they, at the same time, impose rather serious safety limitations as these materials may easily be set off or initiated by heat, impact and/or shock. Generally, efforts directed to reducing one or more of these sensitivities have also resulted in reducing the energetic output of the propellant. Heat sensitivity has proved to be somewhat less of a problem to overcome than impact or shock, however. RDX, for example, has a high shock but relatively low thermal sensitivity.
Plasticizers which have high energy output are known as high energy adjustment/plasticizing compounds (HEAPCs). These include NENAs and other such compounds. In the past, several approaches have been used in an effort to reduce the risks associated with sensitive materials while attempting to minimize the associated reduction in energetic output of the overall composition. One such approach has involved the elimination or very limited use of shock-sensitive high energy adjustment plasticizing compounds such as RDX, HMX and the like. In this manner, these components have been replaced with various other known high energy plasticizer components as plasticizers for nitrocellulose (NC), for example, including nitroglycerine (NG), acetyl triethyl citrate (ATEC) and a variety of nitrated acetals and others with some success.
However, RDX is a low cost primary high energy adjustment component with particularly desirable attributes. These include the ability to increase overall propellant impetus or performance and also to increase the density of the propellant grains which allows for greater bulk loading density in the shell case as compared to conventional propellants in similar geometries. Thus, if the sensitivity of the RDX-containing formulations could be decreased without reducing or eliminating the RDX, formulae with superior performance could be achieved.
RDX has been added to JA-2, conventional tank and artillery propellant in the past to achieve advanced ballistic performance. However, it has been reported that researchers at Army Research Laboratory (ARL) found RDX crystals on the surface of the JA-X propellant during aging. These researchers theorize that the RDX, partially dissolved in the DEGDN fraction, was carried to the surface of the granules as the DEGDN began to leach out at higher temperatures. This crystalline growth on the surface is a significant sensitivity hazard, and greatly increases the likelihood of initiation due to unplanned mechanical stimuli. For this and other reasons, including the inherent sensitive nature of RDX, the use of RDX in artillery propellant compositions, has been generally discouraged.
The use of nitratro ethyl nitramine (NENA) compounds in propellant formulae is known. U.S. Pat. No. 5,482,581 to Urenovitch discloses low vulnerability propellant (LOVA) containing mixtures of alkyl nitrato ethyl nitramines (alykyl NENAs) and/or bis (2-nitroxy-ethyl) nitramine (DINA) with nitrocellulose (NC). A further U.S. Pat. No. to Zeigler, 5,520,756, also discloses the use of alkyl nitrato ethyl nitramine in combination in nitrocellulose/nitroguanidine double based propellants which may also contain cyclonites (RDX).
U.S. Pat. No. 5,325,782 to Strauss et al incorporates a cyclic nitramine in the form of 2-nitroimino-5-nitro-hexahydro-1,3,5 triazine (NNHT) which may be combined with methyl and ethyl NENA, nitrocellulose and RDX. Dillehay et al (U.S. Pat No. 5,487,851) also shows the possible use of alkyl NENA compounds in LOVA propellants which may contain RDX.
It would present an advantage if a significant amount of the low cost high energetic propellant ingredient RDX could be utilized to increase the propellant impetus and loading density in a manner which does not cause the propellant composition to be more sensitive to heat, impact and/or shock. This is especially true with respect to munitions for tank guns.
Accordingly, it is a principal object of the present invention to obtain an insensitive, high energy polybased propellant composition.
It is also a principal object of the present invention to provide a propellant for artillery weapon systems having improved energetic properties with respect to conventional JA-2 without sacrificing safety or increasing the sensitivity threshold initiation levels (TIL).
Another object of the invention is to increase the impetus of propellant compositions by adding a relatively large amount of RDX without increasing the sensitivity of the propellant.
A further object of the invention is to provide artillery propellant matrices containing ethyl and methyl NENA in combination with relatively large amounts of RDX.
A still further object of the invention is to provide artillery propellant matrices including ethyl and methyl NENAs and RDX that offer impetus and shock sensitivity advantages over formulae using NG and DEGDN plasticizers.
Other objects and advantages will become apparent to those skilled in the art upon becoming familiar with the present specification together with the appended claims.